Valve having pressure balancing piston and method involving same

ABSTRACT

A valve assembly is disclosed that provides for complete or partial fluid pressure balancing across the valve, and can be used for reducing valve actuation forces in order to employ electric actuation. The valve assembly includes a valve housing having a valve chamber, a flow passageway, and a piston chamber. A valve member is disposed in the valve housing and is movable along a valve axis. The valve member is subjected to a first pressure, which urges the valve in a first direction. To counteract this force, a piston integral with the valve member is slidably arranged in the piston chamber. One side of the piston is subjected to this first pressure to provide a counterbalancing force. A pressure passage fluid communication of the first pressure between the flow passageway and said one side of the piston.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a divisional of U.S. patent application Ser.No. 10/695,403, filed on Oct. 28, 2003, now U.S. Pat. No. 7,000,895which claims the benefit of U.S. Provisional Patent Application No.60/423,033, filed Nov. 1, 2002, the entire disclosures of which arehereby incorporated by reference.

FIELD OF THE INVENTION

This invention pertains to valves and more particularly to apparatus andmethods for balancing fluid pressures across valves.

BACKGROUND OF THE INVENTION

Plug valves are typically known to place high forces on the actuator.This is due to fluid pressure acting on the end face of the plug. Somevalves will incorporate a passage that is drilled from the nose of theplug to an internal cavity. Pressure in this internal cavity acts on ashoulder on the valve between the plug portion and the stem portion toforce the plug in the downward direction, partially counteracting theforces acting on the plug end face that push the valve upward. Theworking area of this shoulder is equal to the working area of the plugface minus the area of the valve stem. Therefore, the working areaoccupied by the valve stem prevents complete pressure balancing acrossthe valve and only provides for partial balancing, which in turnrequires higher actuator force to achieve performance requirementsand/or results in lower dynamic response. Creating a very small valvestem can reduce the actuator force required. However, the stem must belarge enough to transmit the required actuator loads with margin.

In applications that require quick response, plug valves havehistorically been actuated by hydraulic actuators. Hydraulic actuationprovides a high power density that is not achievable with electricactuation. Along with hydraulic actuation, however, one alsounfortunately gets oil leaks, fire concerns, filtering requirements, oilpiping, and a costly hydraulic power unit. Such hydraulic power unitsmay cost in excess of $50,000 in certain gas turbine applications.

Electric actuation has typically been reserved for low powerapplications: high force at low speeds or low force at high speeds.However, a large number of applications do not fall in these categoriesas end users define valve operating pressures and dynamic responserequirements, which in turn requires the more costly hydraulicactuation. Reduction of plug valve actuation forces is necessary toeconomically applying electric actuators on high performanceapplications, such as valves for turbine fuel metering. Accordingly,there is a desire and need to reduce valve actuation force and/orincrease dynamic valve response in the art.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed toward a valve assembly that canprovide for pressure balancing across the valve, which can be used forexample, for reducing valve actuation forces or increasing dynamicresponse, or both, or for any other suitable purpose (e.g. counteractingflow forces, etc.). The valve assembly includes a valve housing having avalve chamber, a flow passageway extending through the valve chamber,and a piston chamber. A valve member is disposed in the valve housingand is movable along a valve axis. The valve member has a plug portionarranged along the flow passageway for regulating fluid flow. The plugportion is subjected to a first fluid pressure from the flow passagewaythat urges the valve in a first direction. To counteract this force, apiston integral with the valve member is slidably arranged in the pistonchamber. The piston has a first side subjected to this first fluidpressure urging the valve in a second direction opposite said firstdirection. A second side of the piston is subjected to a second fluidpressure which may be lower (e.g. atmospheric pressure) that urges thevalve in the opposing first direction. A pressure passage is provide tocommunicate fluid pressure between the first side of the piston and thevalve plug portion to subject the first side of the piston to the firstpressure.

The present invention is also directed toward a method of balancingfluid forces across a plug valve that comprises:

-   -   regulating a flow of fluid along a flow passageway with a valve        member, the valve member including a plug member that is adapted        to restrict flow and a valve stem, the fluid acting upon the        plug member and being at a first pressure to provide a first        force urging the valve member in a first direction;    -   actuating the valve stem to drive the valve member;    -   counteracting at least part of the first force with a second        force generated by a piston integral with the valve member and        slidable in a piston chamber, the piston having a first side        subjected to the first pressure and a second side vented to        ambient; and    -   communicating the first pressure from the flow passageway to the        piston chamber on the first side.

Other aspects, objectives and advantages of the invention will becomemore apparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a valve assembly in accordance with anembodiment of the present invention, with a fuel metering applicationbeing indicated schematically.

FIG. 2 is an enlarged portion of the cross section of the valve assemblyshown in FIG. 1, with the valve illustrated in a closed position.

FIG. 3 is cross section similar to FIG. 2, but with the valve shown inan open position.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an embodiment of the present invention has beenillustrated as an electrically actuated valve assembly 10. Anapplication or example working environment schematically shown in FIG. 1is metering fuel flow in a turbine engine. As schematically illustratedfor this application, a pump 12 pressurizes and pumps fuel (which mayeither be gaseous fuel or liquid fuel) from a fuel storage tank 14 tothe turbine engine 16. The valve assembly 10 is interposed therebetweenfor controlling fuel flow to the engine 16.

The valve assembly 10 includes a valve housing 20 that is adapted topass the fluid to be regulated and provides the fluid chambers used foreffecting the present invention. In the disclosed embodiment, the valvehousing comprises a valve body 22, a generally cylindrical valve cage24, and a valve bonnet 26, however, it will be appreciated that othervalve housing arrangements can be used as appropriate. In theillustrated embodiment, the valve body 26 defines a flow passageway 28with inlet and outlet ports 30, 32. Fuel or other appropriate fluiddepending upon the application flows through the passageway 28 duringoperation, typically in one direction from the inlet port 30 to theoutlet port 32. The valve cage 24 is mounted to the valve body 26 by athreaded retaining collar 33 screwed to valve body to provide a valvechamber along the flow passageway 28. The valve bonnet 26 is bolted ontothe valve body 26 with spacers and provides a cylindrical bore forguiding valve stroke.

The valve assembly 10 also includes a movable and generally cylindricalvalve member 34 that is mounted for linear reciprocation in the valvehousing 20. The valve member 34 includes a plug portion 38 for providingflow regulation and a stem portion 40 extending axially from the plugportion. The stem and plug portions may be formed as a unitary componentor as separate component parts that may be secured together. The stemportion 40 extends from the valve housing 20 in order to be acted uponby a suitable actuator for positioning the plug portion 38 to regulateflow. The valve member 34 is movable toward and away from a ring shapedvalve seat 42. The valve seat 42 is provided in the valve housing 20between the valve body 22 and the valve cage 24 in a location that iscoaxial about the valve axis 36 and that surrounds the flow passageway28. In the disclosed embodiment, the valve member has a fully openposition as shown in FIG. 3, and a fully closed position in which theplug portion 38 is seated against the valve seat 42, and may includevarious intermediate positions therebetween. It should be noted that inthe disclosed embodiment the fully open position as shown in FIG. 3 isnot set by virtue of the valve member bottoming out, but is setexternally through the actuator that includes a limit to limit how openthe valve member can move. Thus, for all operating positions of thevalve, an internal pressure passage 48, the significance of which isherein described, remains continuously open in the disclosed embodiment.

As shown in FIG. 2, the valve member 34 may include several sections ofdifferent diameters along its axial length. The plug portion 38 includesa cylindrical section with a cone shaped nose that provides a radiallyextending end face 44 and is adapted to seat against the valve seat 42.The stem portion 40 may be of a reduced diameter relative to the plugportion 38 to provide a radially extending shoulder 46 that is adaptedto be acted upon by fluid pressure. The stem portion 40 may also bestepped to include additional different diameter portions as shown.

Since the end face 44 of the plug portion 38 is exposed to the flowpassageway 28, during operation it is subjected to the fluid pressure ofthe fluid in the passageway 28 (which is typically higher than ambient).In the case of high pressure gaseous fuel or pumped liquid fuel in thedisclosed example application, this pressure can be much higher thanambient. Fluid pressure creates an axial force on the valve member 34that urges the valve member 34 in a first direction (e.g. upward in theorientation provided), which in the disclosed embodiment is toward theopen position (although it may also be urged closed under vacuumpressure conditions or alternatively be configured to be urged towardthe closed position). To counteract this pressure induced force, thispressure is ported along a pressure passage 48 to the other side of thevalve plug portion 38. Specifically, the pressure passage 48 ports thepressure experienced at the end face 44 into an intermediate chamber 50defined between the valve stem portion 42 and the valve cage 24, andalso into the opposite end of a piston chamber 52, which may also bedefined by the valve cage 24. In the preferred embodiment asillustrated, the pressure passage 48 includes a first axially extendingpassage segment 54 formed through the movable valve member 34 and secondaxially extending passage segment formed through the cage 26 of thevalve housing 20. However, it will be appreciated that the pressurepassage 48 may be provided entirely through the movable valve member 34or entirely through the valve housing 20 if desired in alternativeembodiments of the present invention.

The fluid pressure that is ported to the intermediate chamber 50 actsupon the working face that is provided by the annular shoulder 46 at theintersection of the valve stem portion 40 and the valve plug portion 38.This provides an axial force opposite the force generated by fluidpressure on the plug end face 44 and partially counterbalances the fluidpressure forces across the valve member 34. However, the effectiveworking area of the annular shoulder 46 is less than the working area ofthe plug end face 44 due to the space occupied by the valve stem portion40. The valve stem 40 projects axially and externally from the valvehousing 20 and is therefore subjected to atmospheric fluid pressure (inaddition to actuator and/or spring force when applied). Accordingly,because the fluid pressure at the plug end face 44 is typicallysubstantially greater than atmospheric, the provision of theintermediate chamber 50 and the annular shoulder 46 is only partiallyeffective in achieving the desired effect.

To provide for a more complete balancing, the disclosed embodimentincludes a piston 58 integral with the valve member 34 that includes afirst side 60 subjected to the fluid pressure experienced at the plugend face 44, and a second side 62 subjected to a second pressure. In theillustrated embodiment this second pressure along the second side 62 ofthe piston is atmospheric pressure by virtue of a vent passage 64 thatvents the lower part of the piston chamber 52 to ambient as a matter ofsimplicity for the disclosed application, although other pressures arepossible (e.g. tank or sump pressure).

With this arrangement, the fluid pressure experienced at the plug endface 44 acts upon the first side 60 of the piston 58 urging the valvemember 34 in a second opposite direction. This provides an axial forceon the valve member 34 independent of the pressure applied at theshoulder 46 due to the fact that a pressure differential exists acrossthe piston 58 by virtue of the second side 62 of the piston 58 beingexposed to a different pressure. Therefore, an alternative embodiment ofthe present invention may eliminate the intermediate chamber 50 and thefluid pressure applied along the shoulder 46. However, in the disclosedembodiment the piston 58 compliments the shoulder 46 and serves thepurpose of offsetting or counterbalancing the working area occupied bythe valve stem portion 40. The effective working area of the of thefirst side 60 of the piston 58 may therefore be about equal to thelargest diameter of the stem portion 40. If desired, a difference inworking areas may be provided to substantially balance the valve whileat the same time, providing a slight bias on the valve such as tomaintain the valve in a closed (or open) position upon power loss, or toprovide a force to counteract other flow forces or to balance springforces, or for any such suitable balancing purpose. With the provisionof the piston 58, however, the fluid pressure forces can more easily becontrolled across the valve member 34 to provide a desired performancecharacteristic which has not been achieved in the prior art, such asreducing actuator force and/or improving dynamic performance.

The integral piston 58 can either be unitarily formed into the valvestem portion 40, or as shown may be a separate component part secured tothe valve member. In the disclosed embodiment, the piston 58 is aseparate ring shaped component with a central hole such that it is thatis concentrically slid onto the valve stem portion 42 and securedthereon by a retaining mechanism. The retaining mechanism used in thedisclosed embodiment is the combination of a shoulder 66 formed at astep in the stem portion 40 and a snap ring 68 that is installed into agroove on the valve stem portion 40. However, it will be appreciatedthat other integral connectors may be used such as a threadedconnection, welding and the like that cause the piston to move with thevalve member 34.

Dynamic or static ring seals 70 as illustrated are strategically locatedin seal retaining grooves throughout the valve assembly 10 to providesealing and to prevent passage of fluid between component parts. Theoperation of such seals will readily be appreciated by one of ordinaryskill in the art upon viewing the drawings, and accordingly furtherdescription is not provided herein for purposes of brevity. However, itshould be noted that if leakage were to occur past any one of many ofthe seals 70 (particularly dynamic seals which are more prone to wear),such leakage paths lead to a common fugitive emission collection passagewhich happens to coincide with the piston chamber vent passage 64. Thisis particularly advantageous for gaseous fuels for which leakageproblems may be hard to detect. The vent passage 64 leads to a fugitiveemission port 74 that may be subjected to atmospheric pressure. The port74 may be connected to a filter or screen to avoid plugging or dirtingress, or for gaseous fuel applications an exhaust line leading to aremote safe exhaust port location for fugitive gas emissions, sensorequipment, or other apparatus.

Also, cylindrical wear rings/bushings 72 supported by the valve housing20 are also provided in spaced axial relation along the valve member 34to guide sliding movement of the valve member 34.

The electrically actuated valve assembly 10 may also include as part ofan overall support housing, not only the valve housing 20, but also aspring housing 76 and an actuator housing 78, as shown in FIG. 1. In analternative embodiment, these structural components parts may not beneeded or may also be integrated into the valve housing 20 whichprovides the various fluid chambers if desired. In the disclosedembodiment, the spring housing 76 is mounted between the actuatorhousing 78 and the valve housing 20. The valve stem portion 40 extendsthrough the valve bonnet 26 into the spring housing 76. Here the stemportion 40 may be biased by one or more springs 80 (e.g. it may bebiased toward a closed, an open position, or may be unbiased), and issubjected to the driving force output 82 of an electrical actuator 84contained in the actuator housing 78.

An advantage that can be realized using the pressure balancing aspectsof the present invention is that a lower power electrical actuator 84may be used and/or dynamic performance can be increased. The piston 58can be used to effectively reduce the pressure imbalance that wouldotherwise occur absent the piston 58 and if only partial counterbalancewas provided via the pressure in intermediate chamber 50 acting uponshoulder 46. Although significant advantages are realized for electricalactuation applications, it will be appreciated that the invention mayalso be employed with other types of actuators including hydraulicactuation where an increase in dynamic performance or decrease inactuation force is desired or for other appropriate purposes. As appliedto the disclosed exemplary application, large stroke forces are notrequired to move the valve member 34 with the pressure balancingcharacteristics afforded by the piston 58, and therefore electricalactuation provided by an electrical actuator 84 can be used for manyapplications that previously used hydraulic actuation.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A method of balancing fluid forces across a plug valve comprising thesteps of: regulating a flow of fluid along a flow passageway with avalve member, the valve member including a plug portion that is adaptedto restrict flow and a valve stem, the fluid acting upon the plugportion and being at a first pressure to provide a first force urgingthe valve member in a first direction; actuating the valve stem to drivethe valve member; counteracting at least part of the first force with asecond force generated by a piston integral with the valve member andslidable in a piston chamber, the piston having a first side subjectedto the first pressure and a second side vented to ambient; communicatingthe first pressure from the flow passageway to the piston chamber on thefirst side; and porting the first pressure to a radially extendingworking surface of the valve member, the first pressure acting upon theradially extending working surface separate from the piston to urge thevalve member in a second direction opposite said first direction tofurther counteract said first force.
 2. The method of claim 1 whereinthe step of actuating the valve stem comprises electrically actuatingwith an electrical actuator driving the valve member.
 3. The method ofclaim 1 wherein the first pressure applied to the first side urges thevalve member in the second direction.
 4. The method of claim 1 furthercomprising the step of metering fuel flow in a turbine engine along theflow passageway with the plug portion.
 5. The method of claim 1 whereinthe step of porting the first pressure is conducted at least in partthrough an internal passage in the valve member and at least in partthrough a housing slidably engaging the valve member.
 6. The method ofclaim 5 wherein the internal passage in the valve member is located inpart along a radial axis of the valve member.
 7. The method of claim 5wherein the internal passage in the valve member is continually open. 8.The method of claim 1 further comprising the step of providing a leakagepath to a common fugitive collection passage.
 9. The method of claim 1wherein the step of actuating the valve stem to drive the valve membercomprises actuating the valve stem to drive the valve member at a lowerstroke force than the stroke force that is required to drive the valvemember without counteracting at least part of the first force with thesecond force.
 10. A method of improving dynamic performance of a plugvalve that regulates flow of fluid along a flow passageway with a valvemember, the valve member including a plug portion that is adapted torestrict flow and a valve stem, the fluid acting upon the plug portionand being at a first pressure to provide a first force urging the valvemember in a first direction, the method further comprising the steps of:actuating the valve stem to drive the valve member; counteracting atleast part of the first force with a second force generated by a pistonintegral with the valve member and slidable in a piston chamber, thepiston having a first side subjected to the first pressure and a secondside vented to ambient; communicating the first pressure from the flowpassageway to the piston chamber on the first side; and porting thefirst pressure to a radially extending working surface of the valvemember, the first pressure acting upon the radially extending workingsurface separate from the piston to urge the valve member in a seconddirection opposite said first direction to further counteract said firstforce.
 11. The method of claim 10 wherein the first pressure applied tothe first side urges the valve member in the second direction.
 12. Themethod of claim 10 further comprising the step of metering fuel flow ina turbine engine along the flow passageway with the plug portion.
 13. Amethod of balancing fluid forces across a plug valve and improvingdynamic performance of the plug valve, the method comprising the stepsof: regulating a flow of fluid along a flow passageway with a valvemember, the valve member including a plug portion that is adapted torestrict flow and a valve stem, the fluid acting upon the plug portionand being at a first pressure to provide a first force urging the valvemember in a first direction; actuating the valve stem to drive the valvemember; counteracting at least part of the first force with a secondforce generated by a piston integral with the valve member and slidablein a piston chamber, the piston having a first side subjected to thefirst pressure and a second side vented to ambient; communicating thefirst pressure from the flow passageway to the piston chamber on thefirst side; and porting the first pressure to a radially extendingworking surface of the valve member, the first pressure acting upon theradially extending working surface separate from the piston to urge thevalve member in a second direction opposite said first direction tofurther counteract said first force, thereby improving dynamicperformance of the plug valve.
 14. The method of claim 13 wherein thesteps of counteracting at least part of the first force with the secondforce and communicating the first pressure from the flow passageway tothe piston chamber on the first side provides the capability to drivethe valve member at a lower stroke force than the stroke force that isrequired to drive the valve member without counteracting at least partof the first force with the second force.
 15. The method of claim 13wherein the first pressure applied to the first side urges the valvemember in the second direction.
 16. The method of claim 13 wherein thestep of porting the first pressure is conducted at least in part throughan internal passage in the valve member and at least in part through ahousing slidably engaging the valve member.
 17. The method of claim 13further comprising the step of providing a leakage path to a commonfugitive collection passage.